1. Field of the Invention
The present invention relates to a new and improved safety system for automatically preventing over pressure in the interior of pneumatically operated devices such as air tools and the like which are supplied from a source of compressed air. Many such tools and pneumatically operated devices have interior air chambers and in particular, fastener driving tools employ hollow handles having an air chamber therein for supplying compressed air to operate the mechanism within the tool body. The present invention is directed towards a safety relief valve system for preventing injury to persons and the surrounding environment in the event that an over pressure or excessively high pressure is inadvertently supplied to the tool. The safety system is automatically resettable so that when the air pressure is reduced back to an acceptable safe level, tool operation may then be continued.
2. Background of the Prior Art
In the past, pneumatic tools and particularly, fastener driving tools have employed blowout plugs in the handle or internal reservoirs thereof so that the inadvertent connection of the tool to a source of compressed air of excessive pressure does not result in explosion or fracture of the tool body or housing and other damage to tee tool, the surrounding environment and operating personnel. However, after a blowout plug is expelled because of excessive pressure, sometimes lengthy servicing of the tool is required before the tool can be put back on the line for continuing operation.
German Patent No. 24 22 223 discloses a compressed air tool having a vent valve therein to protect against back pressure caused by the operating piston moving in the working cylinder. British patent application No. 2,124,537 discloses a pneumatic nailer in which disablement of tool operation occurs when a predetermined main pressure is exceeded. Belgian Patent No. 527,617 discloses a fluid relief valve and the following U.S. Pat. Nos. 1,454,409; 2,530,091; 2,845,085 and 3,542,062 disclose various pressure relief valves and pressure relief systems.
None of the prior art patents provide an automatically resetting safety system for pneumatic tools and the like capable of protecting the tool, environment and personnel from possible damage should the tool be inadvertently connected to a supply of pressurized air at excessive pressure exceeding the design or safe operating pressure of the tool.